The present invention relates to a method of making a product adhere to a surface.
It further relates to the applications of such a method in different fields depending on the nature of the surface and that of the product.
It is very particularly applicable to the treatment of biological surfaces such as human skin or hair, animal skin or fur or the cuticle of plants or insects.
It is also applicable to the treatment of fibers, both natural and artificial, and to fiber-based products such as fabrics.
Different fields of industry are known where it is sought to improve the interaction between a product and a surface or to fix a product to a surface, either in order to improve the state of this surface or in order to subject it to a particular treatment. Particular possible applications are those where it is sought to modify the properties of a surface by subjecting it to a particular treatment with a product which needs to remain in contact with this surface for a sufficiently long time.
It is often useful to be able to treat fibers or textile or natural surfaces in order to improve their appearance (brightness, color, fragrance, etc.) or their properties (wear resistance, elasticity, slip, etc.) or in order to give them new functions.
In the case of skin, body hair/fur and hair, it is often sought to apply active agents thereto which medicate, treat or fortify it, for example.
In general terms, "active agent" or "active product" will be used indiscriminately below to denote the product which it is desired to fix to a surface.
One of the problems encountered in these various treatments is to ensure that the product persists on the surface, whether it be an inert surface or a biological surface such as the skin, body hair/fur, hair or integuments of living beings or the surface or cuticle of plants. Very often, the treatment is applied by means of a chemical reaction or by physicochemical adsorption (for example dyeing) during the manufacture of the fiber, or by means of a treatment requiring a special application in the case of human hair.
If an attempt is made to apply the treatment during a washing operation or when shampooing, for example, the main problem encountered is the fact that the active agent delivered by the shampoo or the detergent product, which is rinsed off, is very largely lost, only a tiny fraction remaining fixed to the treated surface. The persistence is therefore low, even if the proportion of active agent in the product is high. The same type of problem can arise if the treated surface is then exposed to the action of rain, for example.
Microencapsulation is a solution commonly used to prolong the period of availability of an active agent by only releasing it slowly. It is usually effected by forming a polymer shell around the active principle, either by spraying the active agent in the presence of a polymer or by one of the numerous encapsulation methods developed in industry, such as the various techniques of coacervation, atomization and coprecipitation. Liposomes can also be used, but their low stability and their cost prevent them from being used industrially.
International patent application WO 95/23578 describes the use of cationic liposomes for depositing an active ingredient on hair. The main problem presented by such liposomes is that the technique used to prepare them, which is simply to add the components of the liposomal membrane to the solution of active agent, does not easily allow control over the degree of encapsulation, which in any case is always low. Furthermore, only water-insoluble active agents can be encapsulated in such liposomes, thereby considerably limiting the list of active products suitable for use in such a technique.